Hortus III lists around 100 different species in the northern hemisphere! 'Froebelli' is a cultivar like 'Anthony Waterer,' both of which are crosses of Spiraea albiflora and S. japonica. 'Snowmound' is a cultivar of S. nipponica (Tosa spiraea).

There are innumerable crosses and variations within different species of spiraea. But of the three you listed Froebel and Goldmound tend to have unbranched to lightly branched stems where Snowmound is branched with heavier stems.

As far as shade tolerance, A. W. has tolerated considerable shade in my yard, but certainly does fine in full sun. There are undoubtedly others with good shade tolerance. A. W. is slightly smaller than Froebel at maturity but has more intensely colored blooms. Disease-wise, a few feet from the A. W. all of my Snowmounds have been affected by what I'm guessing to be bot canker, two have died and the other three are so badly damaged that they will be shovel pruned this spring. The A. W.'s are not affected by this at all. I also have a hedge of S. x vanhouttei and a single plant of S. prunifolia in the yard that are not affected, leading me to think that Snowmound is a weaker species.

Snowmound gets much taller than the other two, but the time from planting to mature size is probably similar.

Spiraeas are generally pretty tough plants for this area (and many others!).

hortster

Spirea nipponica 'Snowmound' is the most worthless, crappy, dieback shrub I've ever encounter.

Most cultivars of Spirea japonica are just all around champs.

Spiraea fritschiana is a very nice species but prefers cooler/moist enviroments.

Spiraea betulifolia 'Tor' is one of the most impressive classic Spirea there is.

How about Spirea japonica 'Shirobana'. have either of you had any experience with this cultivar?

Nope. I've seen it in this area but not grown it. Interesting multi-colored blooms. There are so many different spiraeas that you could landscape an entire yard with just them.

I've always stuck to the old proven species and varieties, pretty much trouble free.

hortster

Hmmm...maybe I'll try it and plant one in morning sun and afternoon shade and one in full sun. Then I'll let you know how they do.